Ultrasound imaging and pulse-echo technology has been widely used in the medical field for therapy, diagnostic testing and evaluating pregnancies. It has also been widely used for evaluating castings, forgings and other structures with regards to delamination, voids, cracks, weld integrity and other indicators of structural integrity. Furthermore, ultrasonic technology has application in evaluating seal integrity spoilage or contamination in food products.
A major factor in the successful application of ultrasound testing is the establishment of an interface between the ultrasound probe and the surface/skin of the item/person to achieve the best possible impedance match and minimize signal loss. This interface is commonly achieved by applying an ultrasound transmission gel to the surface/skin of the item/person which will receive the ultrasound waves, and then bringing an ultrasound probe into contact with the gel. A continuous flow of water between the surface of an object and an ultrasound probe which acts as a bridge for ultrasound waves has been employed as a couplant in industrial applications for evaluating structures. Immersion of the object being tested in water to act as a couplant is also commonly practiced.
Ultrasound transmission gels are available in squeeze bottles, foil packs, bulk containers and gel pads. These gels are relatively expensive, and their use is messy and labor intensive. The use of a liquid spray as an ultrasound couplant requires relatively sophisticated and expensive equipment, and of course the use of a liquid can be result in overflows and spills.
One approach to the elimination of gels or flowing liquids as acoustical couplants is a dry couplant pad made-of a compliant encapsulated epoxy material attached as a facing to an ultrasonic-transducer wedge. However, such a solid couplant material has a lower ultrasound transmission efficiency than a liquid or gel couplant. "Shear-Wave Ultrasonic Inspection With a Dry Couplant", NASA Tech Briefs, Dec. 1994, pp. 77-78.
There is provided in accordance with the present invention an apparatus for ultrasound testing which does not require the use of an acoustic transmission gel, does not entail the usual drawbacks of a liquid couplant while in fact employing a liquid couplant, and does not have the drawbacks of a dry couplant material because a liquid couplant is employed.